Display device

ABSTRACT

In a display device including, a display area having a plurality of organic EL devices on a substrate; a peripheral area having a driving circuit for the organic EL devices and surrounding the display area on the substrate; and an organic insulating film covering at least the driving circuit, the organic insulating film has a separating groove which divides itself into the inner part and outer part at the periphery of the display area.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP2004-235125 filed in the Japanese Patent Office on Aug.12, 2004, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device and particularlyrelates to a display device suitable for the application to an organicEL display device.

2. Description of the Related Art

An organic EL device containing an organic material, electroluminescence(called EL hereinafter), is now popular as a light-emitting device,which can emit high intensity light through low-voltage direct-currentdriving. However, in such a device including organic EL devices (thatis, an organic EL display device), moisture may deteriorate an organiclayer of the device, which may lower the intensity of emitted light ineach of the devices and/or may cause unstable light emission.

Conventionally as shown in FIG. 6, the organic EL devices on thesubstrate 101 are sealed by a cover member 102 and a sealant 103. Also,a rigid carbon film may be further provided at the outside of thesealant 103. Thus, the organic EL devices on the substrate 101 can beshielded from the outside, especially from moisture and oxygen which maycause the oxidization of the organic EL devices and prompt thedeterioration of the devices (see Patent Document 1 below).

In FIG. 7, the cover member 102 is bonded via an adhesive 105 onto adevice side 101 a of the substrate 101 having organic EL devices and/ora circuit.

Patent Document 1: JP-A-2002-93576

SUMMARY OF THE INVENTION

However, in such devices, the spread of the moisture remaining withinthe display device is not completely prevented.

In particular, an inter-layer insulating film covering a driving circuitis made of an organic photo-sensitive material and allows water to passthrough easily. Therefore, the moisture left within the display deviceeasily spread via the inter-layer insulating film.

Accordingly, it is desirable to propose a display device which canprevent the deterioration of organic EL devices due to the spread ofmoisture remaining within the display device for higher long-termreliability.

According to an embodiment of the present invention, there is provided adisplay device including, a display area having a plurality of organicEL devices on a substrate; a peripheral area having a driving circuitfor the organic EL devices and surrounding the display area on thesubstrate; and an organic insulating film covering at least the drivingcircuit, the organic insulating film has a separating groove whichdivides itself into the inner part and outer part at the periphery ofthe display area.

In such a device, the separating groove divides the organic insulatingfilm into the inner part and outer part. Therefore, the deterioration ofthe organic EL devices due to moisture in the display area can bereduced by preventing moisture in the outer part of the organicinsulating film from moving into the inner part of the organicinsulating film. The separating groove is preferably provided betweenthe display area and the peripheral area, so that the moisture in theperipheral area is prevented from moving into the display area throughthe organic insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams showing a construction of a display deviceof a first embodiment;

FIGS. 2A and 2B are main part enlarged section views showing aconstruction of the display device of the first embodiment;

FIGS. 3A and 3B are main part enlarged section views showing aconstruction of a display device of a second embodiment;

FIGS. 4A and 4B are diagrams showing a construction of a display deviceof a third embodiment;

FIG. 5 is a schematic section view showing a construction of a displaydevice of a fourth embodiment;

FIG. 6 is a schematic section view showing a construction of a displaydevice in the past; and

FIG. 7 is a schematic section diagram showing another construction of adisplay device in the past.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a display device of the invention will be described belowin detail with reference to drawings.

First Embodiment

FIG. 1A is a plan view showing a construction of a display device of afirst embodiment, and FIG. 1B is a schematic section view taken at LineA-A′ in FIG. 1A.

First of all, as shown in the plan view in FIG. 1A, a display device 1is an organic EL display device including organic EL devices EL servingas light emitting elements. On a substrate (which is a supportingsubstrate here) 2, the display device 1 includes a display area 3, aperipheral area 4 surrounding the display area 3, and an implementedarea 5. The substrate 2 is made of a transparent material such as glass.The display area 3 has a plurality of organic EL devices EL. An IC chipand/or a circuit substrate are implemented on the implemented area 5.

In the display area 3, each of pixels on the supporting substrate 2 hasan organic EL device EL. When the display device 1 is an active-matrixdisplay device, each pixel has an organic EL device and a pixel circuit(not shown) for driving the organic EL device. Each of the pixelcircuits has a thin-film transistor serving as a switching element.

The peripheral area 4 surrounding the display area 3 has drivingcircuits (not shown) for transmitting a scan signal and/or a data signalto the organic EL devices EL. Each of the driving circuits includes athin-film transistor. The driving circuits in the peripheral area 4 areconnected to each other.

The implemented area 5 may have an array of terminals 6 for inputting anexternal signal to the driving circuits in the peripheral area 4, forexample.

The display device 1 including the display area 3, peripheral area 4 andimplemented area 5 as described above has the construction as shown inFIGS. 1A and 1B. In other words, a circuit-formed layer 11 (shown in thesection view only) is provided on the supporting substrate 2. Thecircuit-formed layer 11 has the pixel circuits in the display area 3 anddriving circuits in the peripheral area 4. An organic insulating film 12covers the circuit-formed layer 11 on the supporting substrate 2. Here,the organic insulating film 12 serves as a flattening insulating film.

An EL layer 13 (shown in the sectionview only) is provided on thesurface flattened by the organic insulating film 12. The EL layer 13 hasa plurality of organic EL devices EL. An inorganic insulating film 14(shown in the section view only) covers the organic EL devices EL (thatis, EL layer 13) in the display area 3 and peripheral area 4. Notably,the implemented area 5 does not have the inorganic insulating film 14.

The display area 3 and peripheral area 4 covered by the inorganicinsulating film 14 further have an adhesive layer 15 (shown in thesection view only). The supporting substrate 2 is bonded to an oppositesubstrate 17 through the adhesive layer 15 so that the organic ELdevices EL in the display area 3 can be sealed. The adhesive layer 15contains an extremely low pervious material.

In the plan view in FIG. 1A, a part of the organic insulating film 12and opposite substrate 17 is cut out for easy description.

In the display device 1 of the first embodiment having this layerstructure as described above, the organic insulating film 12 has aseparating groove a. The separating groove a separates the organicinsulating film 12 into an inner part 12 a and outer part 12 b.

The separating groove a is a groove-shaped part resulting from thecomplete removal of the organic insulating film 12 and at leastsurrounds a part of the display area 3 and preferably surrounds theentire circumference of the display area 3. The separating groove a isfurther preferably provided between the display area 3 and theperipheral area 4 as shown in FIG. 1A.

FIG. 2A shows an enlarged section view of Part B in the schematicsection diagram in FIG. 1B, and FIG. 2B shows an enlarged section viewof Part B′ in the schematic section view in FIG. 1B. Note that Parts Band B′ overlap one another in the depth direction in FIG. 1B. Detailedlayer structures of the separating groove a and the surrounding will bedescribed with reference to FIGS. 1A and 1B and based on the enlargedsection views in FIGS. 2A and 2B.

As shown in FIG. 2A, the display area 3 and peripheral area 4 on thesupporting substrate 2 have thin-film transistors Tr included in thepixel circuit and driving circuits, and an inorganic insulating film 21covers the thin-film transistors Tr therein. A wiring 25 is provided onthe inorganic insulating film 21. The wiring 25 is connected to asemiconductor layer 23 included in the sources and drains of thethin-film transistors Tr through connection holes 21 a in the inorganicinsulating film 21. The thin-film transistors Tr and wiring 25 areincluded in the pixel circuits of the display area 3 and the drivingcircuits of the peripheral area 4. These components described up to thispoint are included in the circuit-formed layer 11 described withreference to FIG. 1B.

A first organic insulating film 27 covers the wiring 25 on the inorganicinsulating film 21. The first organic insulating film 27 contains aphoto-sensitive compound and is coated as a flattening insulating film.The first organic insulating film 27 has a separating groove al betweenthe display area 3 and the peripheral area 4 so that the display area 3is surrounded. The separating groove al is formed by lithographyprocessing.

The display area 3 on the first organic insulating film 27 has aplurality of organic EL devices EL. The organic EL devices EL have alower electrode 31 connecting to the wiring 25 through a connection hole27 a in the first organic insulating film 27. The lower electrode 31 isto be used as an anode (or cathode) and is patterned as a pixelelectrode. The periphery of the lower electrode 31 is covered by asecond organic insulating film 33 and is widely exposed at the centerpart only. The second organic insulating film 33 may contain aphoto-sensitive compound, for example. Lithography processing is used toform an opening above the lower electrode 31 and a separating groove a2over the separating groove al of the first organic insulating film 27.

Thus, according to the first embodiment, the first organic insulatingfilm 27 and the second organic insulating film 33 are included in theorganic insulating film 12 described with reference to FIGS. 1A and 1B.The separating groove al in the first organic insulating film 27 and theseparating groove a2 in the second organic insulating film 33 form theseparating groove a described with reference to FIGS. 1A and 1B.

An organic layer 35 including a light-emitting layer at least ispatterned and stacked on the lower electrodes 31 exposing from thesecond organic insulating film 33. The light-emitting layer in theorganic layer 35 contains an organic material, which emits light inresponse to the re-coupling of positive holes and electrons implanted tothe light-emitting layer. An upper electrode 37 is provided on thepatterned organic layer 35 and the second organic insulating film 33.Here, the upper electrode 37 is isolated from the lower electrode 31.The upper electrode 37 is to be used as a cathode (or anode), isprovided as an electrode common to the organic EL devices EL and coversthe display area 3.

Here, the EL layer 13 described with reference to FIG. 1B is the layerhaving a plurality of organic EL devices EL in the construction asdescribed above.

The inorganic insulating film 14 and adhesive layer 15 cover the organicinsulating film 12 and organic EL devices EL, and the opposite substrate17 is provided thereon.

As shown in FIG. 2B, the upper electrode 37 for the organic EL devicesEL has an end extending as an upper electrode wiring 37 a in theperipheral area 4 and connecting, at predetermined positions, to thedriving circuits in the peripheral area 4. Thus, the upper electrodewiring 37 a extends to the peripheral area 4 across the separatinggroove a surrounding the display area 3. Therefore, securing an enoughthickness of the organic insulating film 12 (that is, the first organicinsulating film 27) is important for maintaining isolation between thewiring 25 in the display area 3 and the peripheral area 4 and the upperelectrode wiring 37 a.

At place where the upper electrode wiring 37 a crosses the separatinggroove a, the wiring 25 in the display area 3 and the wiring 25 in theperipheral area 4 are connected through a connection wiring below theinorganic insulating film 21. In this case, for example, thesemiconductor layer part of the same layer as the semiconductor layer 23included in the thin-film transistors Tr may be a connection wiring 23 aso that the connection wiring 23 a can connect the wiring 25 in thedisplay area 3 and the wiring 25 in the peripheral area 4. Thus, thewiring 25 in the display area 3 and the wiring 25 in the peripheral area4 can be connected each other without a short circuit with respect tothe electrode wiring 37 a.

In display device 1, the separating groove a in the organic insulatingfilm 12 surrounding the display area 3 divides the organic insulatingfilm 12 into the inner part 12 a and the outer part 12 b, as describedwith reference to FIGS. 1A and 1B and 2A and 2B. Thus, the moistureexisting in the part corresponding to the outer part 12 b of the organicinsulating film 12 does not enter into the inner part 12 a through theorganic insulating film 12. Therefore, the deterioration of the organicEL devices EL due to moisture can be prevented in the display area 3positioned at the part covered by the inner part 12 a.

In particular, the separating groove a surrounding the display area 3and between the display area 3 and the peripheral area 4 can prevent theentry of the moisture existing in the peripheral area 4 having thedriving circuits into the display area 3 through the organic insulatingfilm 12. Therefore, even when moisture is absorbed to a foreign material(such as dust) caused in a process of manufacturing the driving circuitsin the peripheral area 4, the entry of the moisture into the displayarea 3 can be prevented, which can further prevent the deterioration ofthe organic EL devices more effectively. Preferably, the separatinggroove a is provided surrounding the display area 3 as closely aspossible to the display area 3. Thus, the volume of the inner part 12 aof the organic insulating film 12 can be reduced, and the amount ofmoisture that reaches to the organic EL devices EL through the part canbe therefore reduced.

As a result, the long-term reliability of the display device 1 can beachieved since the deterioration of the organic EL devices EL due tomoisture can be prevented.

Second Embodiment

FIGS. 3A and 3B are main part enlarged section views showing features ina display device according to a second embodiment. FIG. 3A shows anenlarged section view corresponding to Part B in the schematic sectionview in FIG. 1B, and FIG. 3B shows an enlarged section viewcorresponding to Part B′ in the schematic section view in FIG. 1B. Adisplay device 1 a according to the second embodiment shown in FIGS. 3Aand 3B is different from the display device according to the firstembodiment in that an inorganic layer 41 is provided at the bottom ofthe separating groove a for alleviating the degree of the level changedue to the separating groove a. The other construction of the secondembodiment is the same.

The inorganic layer 41 has a width W1, which is wider enough than thewidth W of the opening at the bottom of the separating groove a. Thebottom of the separating groove a is configured to securely position onthe inorganic layer 41 only so that the degree of the level change dueto the separating groove a can be evenly alleviated. The inorganic layer41 may be formed by patterning the same layer as that of the wiring 25in the display area 3 and peripheral area 4. In this case, the inorganiclayer 41 may be patterned with sufficient isolation from the wiring 25.

In particular, as shown in FIG. 3B, the upper electrode wiring 37 a isconnected and wired to the inorganic layer 41 containing the samematerial as that of the wirings 25 in the part where the upper electrodewiring 37 a extending from the upper electrode 37 for the organic ELdevices EL crosses the separating groove a.

Note that the inorganic layer 41 may contain an insulating material.Also in this case, the inorganic layer 41 has the width W1, which iswider enough than the width W of the opening at the bottom of theseparating groove a, and the bottom of the separating groove a isconfigured to securely position on the inorganic layer 41 only.

Since the separating groove a of the organic insulating film 12 isprovided between the display area 3 and peripheral area 4 also in thisconstruction, the deterioration of the organic EL devices EL due tomoisture in the display area 3 can be prevented like the firstembodiment.

Furthermore, this embodiment has the inorganic layer 41 at the bottom ofthe separating groove a so that the degree of the level change due tothe separating groove a can be alleviated. Thus, the stress on the partcovering the level change due to the separating groove a can bealleviated in the inorganic insulating film 14 on the organic insulatingfilm 12. Therefore, the occurrence of a crack due to the stress can beprevented, which can prevent the entry of moisture through the crack.

The alleviation of the degree of the level change due to the separatinggroove a can easily secure the thickness of the upper electrode wiring37 a extending to the peripheral area 4 across the separating groove a.Thus, the increase in resistant value and/or break of the upperelectrode wiring 37 a can be prevented in the side walls of theseparating groove a.

Notably, the inorganic layer 41 for alleviating the degree of the levelchange due to the separating groove a can be provided without anyincrease in number of steps when the inorganic layer 41 is formed bypatterning the same layer as that of the wiring 25 in the display area 3and peripheral area 4.

Third Embodiment

FIG. 4A is a plan view showing a construction of a display deviceaccording to a third embodiment, and FIG. 4B is a schematic section viewtaken at Line A-A′ in FIG. 4A. A display device lb shown in FIGS. 4A and4B is different from the display devices of the embodiments above inthat a sealed area 45 resulting from the removal of the organicinsulating film 12 is provided in the outermost circumference of thepart having the opposite substrate 17 over the supporting substrate 2,and the other construction is the same.

In other words, in the display device 1 b, the separating groove aresulting from the removal of the organic insulating film 12 is providedbetween the display area 3 and the peripheral area 4 so that the displayarea 3 is surrounded. The sealed area 45 resulting from the removal ofthe organic insulating film 12 is provided surrounding the separatinggroove a and the perimeter of the peripheral area 4. The sealed area 45is the outermost periphery of the part having the opposite substrate 17over the supporting substrate 2 as described above. The outer part 12 bof the organic insulating film 12 separated by the separating groove ahas the both side walls and top face completely covered by the inorganicinsulating film 14 (shown in the section view only) on the organicinsulating film 12 and are sealed by the adhesive layer 15 (shown in thesection view only). In other words, the organic insulating film 12 isnot exposed to the outside in the part between the supporting substrate2 and the opposite substrate 17.

In display device 1 b, the deterioration of the organic EL devices ELdue to moisture in the display area 3 can be prevented like the firstembodiment since the separating groove a of the organic insulating film12 is provided between the display area 3 and the peripheral area 4.

Furthermore, in the display device 1 b of the third embodiment, thesealed area 45 resulting from the removal of the organic insulating film12 and being provided at the outer edges of the supporting substrate 2and opposite substrate 17 can prevent the entry of moisture from theoutside of the display device 1 b. Thus, the deterioration of theorganic EL devices EL due to moisture in the display area 3 can be moresecurely prevented, and the corrosion of a metallic material due tomoisture, for example, can be also prevented in the peripheral area 4.

Fourth Embodiment

FIG. 5 is a schematic section view showing a construction of a displaydevice according to a fourth embodiment. A display device 1 c in FIG. 5is different from the display device of the third embodiment in that ahollow part exists between the supporting substrate 2 and the oppositesubstrate 17, and the other construction is the same.

In other words, in the display device 1 c, an adhesive sealant 47 isprovided between the supporting substrate 2 and the opposite substrate17 surrounding the separating groove a between the display area 3 andthe peripheral area 4 and the perimeter of the peripheral area 4,resulting from the removal of the organic insulating film 12. Thesealant 47 bonds the opposite substrate 17 to the supporting substrate 2and seals the hollow part between the supporting substrate 2 and theopposite substrate 17.

Also in the display device 1 c of the fourth embodiment, thedeterioration of the organic EL devices EL due to moisture in thedisplay area 3 can be prevented, and the reliability can be improvedsince the separating groove a of the organic insulating film 12 isprovided between the display area 3 and the peripheral area 4.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A display device comprising: a display area having a plurality of organic EL devices on a substrate; a peripheral area having a driving circuit for the organic EL devices and surrounding the display area on the substrate; and an organic insulating film covering at least the driving circuit, wherein the organic insulating film has a separating groove which divides itself into the inner part and outer part at the periphery of the display area.
 2. The display device according to claim 1, wherein the separating groove is provided between the display area and the peripheral area.
 3. The display device according to claim 1, wherein: an organic insulating film is further provided as a flattening insulating film embedding the driving circuit on the substrate; the organic EL devices are provided on the organic insulating film; and an inorganic layer is further provided so as to reduce a gap produced by the separating groove.
 4. The display device according to claim 3, wherein: the inorganic layer is made of an insulating material; and an upper electrode for the organic EL devices is provided between the organic insulating film and the inorganic insulating layer and extends to the peripheral area.
 5. The display device according to claim 3, wherein: the inorganic layer is formed as a part of a circuit of the peripheral area; and an upper electrode for the organic EL devices and the inorganic layer extend to the peripheral area.
 6. The display device according to claim 1, wherein a wiring disposed in the inner part and the wiring disposed in the outer part are connected by a wiring disposed under the organic insulating film. 